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Abstract / Poster: 2-4 Clinical MEG: Auditory function Poster: 2-4 Clinical MEG: Auditory function

2-4-1: Superior temporal gyrus M100 phase-locking in schizophrenia: Associations with medication type
and patient symptom profile
*J. Christopher Edgar1,2, Bruce I. Turetsky3, Timothy P.L. Roberts1, Jose M. Canive2,4, Gregory A. Miller4,5 1Dept. of Radiology, The Children's Hospital of Philadelphia, PA, USA 2Center for Functional Brain Imaging, New Mexico VA Healthcare System, Albuquerque, NM, USA 3Dept. of Psychiatry, The Hospital of the U. of Pennsylvania, PA, USA 4Dept. of Psychiatry, U. of New Mexico, Albuquerque, NM, USA 5Depts. of Psychology and Psychiatry and Beckman Institute, U. of Illinois at Urbana-Champaign, EEG/MEG studies have observed an abnormally small 100 ms auditory response in patients with schizophrenia (Sz). A
recent MEG study found that a decreased superior temporal gyrus (STG) auditory M100 response in Sz was best
predicted by decreased phase locking (Edgar et al., 2008). It is unknown whether medications might normalize phase
locking (PL). The present study examined whether STG phase locking (PL) in patients differs as a function of
medication. Associations between STG PL and patient symptoms were also examined.
Dense-array MEG from 45 controls and 45 patients with Sz produced left- and right-hemisphere STG 100 ms PL
measures. Measures of positive and negative symptoms were obtained (PANSS and SANS). Patients on typical
antipsychotics (haldol and prolixin) showed decreased left-hemisphere theta-band PL compared to controls and
compared to patients on atypical antipsychotics (aripriprazole, olanzapine, risperidone, quetiapine). Left-hemisphere PL
did not differentiate controls and patients on atypicals. In the right hemisphere, a trend for decreased PL was observed
in both antipsychotic groups. A significant quadratic relationship between left- and right-hemisphere theta-band PL and
patient symptoms indicated that the more patients' PL values diverged from the mean PL value observed in controls, the
more impaired were the patients (higher PANSS Negative and higher SANS Total scores). Findings suggest that
normalization of theta-band PL would be a promising target of treatment in patients with Sz.
2-4-2: Residual auditory function detected by MEG but not ABR in a patient of minimally conscious state
*Akitake Kanno1, Nobukazu Nakasato1, Tetsuaki Kawase2, Yoshihide Nagamine1, Satoru Fujiwara1 1Kohnan Hospital, 2Tohoku University Graduate School of Medicine Background: Auditory brainstem response (ABR) provides an objective method to evaluate auditory function, but has
failed to detect any response in several patients with whom verbal conversation was possible. The underlying
mechanism of such cases remains unknown. Here we report a case of minimally conscious state with no ABR but
almost normal auditory evoked fields (AEFs). Case: A 69-year-old male had suffered severe head injury in a traffic
accident. The patient was transferred to the emergency unit of another hospital in a deep coma. Initial imaging studies
revealed diffuse axonal injury, contusion of the bilateral fronto-temporal lobes, and traumatic subarachnoid hemorrhage.
After conservative therapy, the patient remained in a minimally conscious state and was transferred to our hospital 7
months after the accident. Methods: ABR stimulated by clicks and AEFs by tone bursts were measured according to the
guidelines of the Japan Clinical Neurophysiology Society [1, 2]. Results: ABR detected no response to monaural or
binaural stimuli. AEFs showed no response to left ear stimuli, but almost normal responses to right ear stimuli, with
clear bilateral N100m peaks at the latencies of 90.8 and 128.5 ms in the left and right hemispheres, respectively.
Equivalent current dipoles were estimated on the posterior part of the upper temporal surfaces. Discussion: Previous
patients with residual hearing function but no ABR were considered to have auditory neuropathy or auditory nerve
diseases with unknown etiology or mechanism. The present and our previous report [3] indicate that AEFs are useful to
evaluate psychological hearing level quantitatively and objectively.1) Shimokochi M, et al. Jap J Clin Neurophysiol 25:
1-16, 19972) Hashimoto I, et al. Jap J Clin Neurophysiol 33: 69-86, 20053) Sasaki T, et al. Neuroimage 25: 684-9, 2005
2-4-3: Neuromagnetic auditory activity reflects differences between normal aging, MCI and AD subjects:
An oddball study
*Selma Supek1, Sanja Josef Golubic1, Jennifer Bryant2, Chris Donahue2, Rebecca Montano2, John Adair3, Blaine Hart2, Janice Knoefel4, Julia Stephen5, Cheryl J Aine2 1University of Zagreb, Faculty of Science, Department of Physics, Zagreb, Croatia, 2Radiology, UNM School of Medicine, Albuquerque, NM 87131, 3Neurology, New Mexico VA Health Care System, Albuquerque, NM 87108, 4Internal Medicine, New Mexico VA Health Care System, Albuquerque, NM 87108, 5The MIND Institute, Albuquerque, NM 87131 Neuromagnetic techniques and a simple auditory oddball task were used to examine alterations in cortical activity of patients diagnosed as MCI and AD relative to age-matched healthy elderly. MEG data were recorded with a CTF 275- channel whole-head system in a magnetically shielded room at the MIND Institute. The participants were: healthy Abstract / Poster: 2-4 Clinical MEG: Auditory function
elderly volunteers, 9 males and 2 females (64-87 years), 3 MCI and 6 AD patients. T1-waighted anatomical MRIs were
obtained for each participant on a Picker Edge 15.T scanner. All participants were given a set of neuropsychological
exams. Auditory oddball task consisted of 400 frequent (1.000 Hz, p=0.8) and 100 rare (1.200 Hz, p=0.2) binaurally
presented tones. Stimulus duration was 200ms, rate of presentation was 1 Hz with an ISI jitter range of 200ms.
Temporal dynamics and source localizations were estimated for two intervals, 0-200 ms and 150-800 ms, using the
Calibrated Start Spatio-Temporal (CSST) program within the MRVIEW. Preliminary results demonstrating differences
in the cortical activation pattern between the three categories of participants include: unilateral early medial temporal
lobe (MTL) activation for rare stimuli in AD compared to bilateral activation in healthy elderly and MCI; lack of early
frontal activity in AD patients to both frequent and rare stimuli; reduced and/or altered MTL late activity for both rare
and frequent stimuli in MCI and AD patients relative to healthy elderly.
2-4-4: Mismatch fields elicited by irregularities in repeated basic rhythm patterns
1Graduate School of Information Environment, Tokyo Denki University, 2Tokyo Denki University To investigate the human neurophysiological process of perception of rhythm in music, we measured evoked magnetic fields elicited by simple rhythm patterns. We expected that the perception of rhythm would depend on the number of
repetitions of the rhythm pattern and that the degree of establishment of the rhythm in the listener would be measured
by the mismatch field as mentioned below.
The basic rhythm pattern was a simple repetition of a downbeat(D)(strong beat)followed by an upbeat(U)(weak
beat)thus comprising the meter in two. The SOA between consecutive beats was 250 ms and hence the tempo was 240
beats/min.
Exp.1
The standard stimulus(80% in frequency) was the basic pattern repeated twice(D U D U)which we designate 2b, b for
basic. The deviant stimulus(20%)was the basic pattern followed by two upbeats(D U U U)which we call 1b+d, d for
deficient.
Exp.2
The standard stimulus was the basic pattern repeated three times(D U D U D U)which we designate 3b. The deviant
stimulus was "D U D U U U" which we call 2b+d.
In a similar way.
Exp.5
The standard stimulus was the basic pattern repeated six times(D U D U D U D U D U D U)which we designate 6b.
The deviant stimulus was "D U D U D U D U D U U U" which we call 5b+d.
The amplitude of MMF increased with the number of repetitions of the basic pattern until it reached the maximum at
4(or 5)repetitions depending on the participants and then decreased. The result suggests that the basic pattern is fixed on
the listener to a stronger degree as the repetition number increases because the larger MMFs are considered to reflect
stronger expectation(of a downbeat)in the listener and that the fixation of the pattern becomes saturated at around 5
repetitions.
2-4-5: Directed Coherence in the Resting Tinnitus Brain
*Winfried Schlee1, Thomas Hartmann1, Nadia Mueller1, Isabel Lorenz1, Sarang S. Dalal2, Nathan Weisz2 1Department of Psychology, University of Konstanz, Germany, 2INSERM U 821, Lyon, France Objective: Tinnitus is defined as the phantom perception of sound in the absence of a physical source. Consequently, in the resting state, tinnitus patients distinguish themselves from control subjects by having a conscious perception of a sound. We hypothesized that the difference between these groups is marked by long-range bi-directional synchronization in the gamma frequency range. Methods: In a sample of 26 chronic tinnitus patients (mean age: 45 years, range: 20-65) and 21 control subjects (mean age: 35 years, range: 23-78) we recorded 5 minutes of spontaneous activity with a 148-channel whole-head MEG system. We used a LCMV-beamformer method to project the sensor data to source space and applied a multivariate autoregressive model to the full grid of voxels (voxel size = 2 cm). We took advantage of the Partial Directed Coherence (PDC) to estimate the directed coherence between voxels in the gamma frequency range. Incoming and outgoing connections were analyzed separately. Results: Preliminary results suggest an increase of incoming gamma connections for the auditory cortices. Outgoing (i.e. driving) connections of the same frequency band were increased in parietal, frontal, and temporal areas. Conclusion: We found support for the hypothesis of bidirectional long-range synchronizations in the gamma range. Thus, perception of an ongoing tinnitus perception is associated with persistent activity in recurrent cortical loops.

Source: http://www.ec-pro.co.jp/biomag2008_abstract/biomagpdf/2-4.pdf